Bob McDavitt's ideas for sailing weather around the South pacific

03 January 2016

Bob Blog



Issued 03 January 2016

Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the patterned world.


This El Nino may be starting to relax now.  The weekly value of the SOI index has relaxed over the last few weeks as seen at

The heat stored in the eastern equatorial Pacific Ocean is measured by the NINO3.4 parameter and this has reached a monthly value of 3.0 in December 2015, exceeding the monthly values recorded in the previous extreme El Nino of 1997/1998 . As seen at


Tropical Cyclones

Tropical cyclone ULA brought storm force winds to Vava’u but these were from the east and the Vava’u group is reasonably well sheltered from that direction, and its hilly terrain sort of knocked ULA a bit. Some minor damage was shown on SBS News on twitter.

ULA is now slowing down and although it may weaken on Monday, it still has the possibility of developing later this week  Fiji Met service are tracking this Cat3 system as it travels across southern Lau group tonight.

So far there have been three fatalities reported and several people are missing.

The latest track map has it possibly turning NW again by Wednesday and that may allow the system to redevelop.

For an update on this track see



Weekly rain maps for the tropics over the past two weeks show a build-up of rain intensity to the NW of Fiji. 




SPCZ=South Pacific Convergence zone.

The SPCZ is expected to remain active to north of 5S with the near- equatorial westerlies and also between Samoa and Tahiti.  There is a good chance that a tropical Low may develop near 15S 153W by Wednesday UTC (local Tuesday) and then deepen and move towards between Tahiti and

Southern Cooks by this weekend.   Keep checking, as we are approaching a summit of activity for this cyclone season according to the MJO. 


STR= Sub-tropical Ridge

Next HIGH to travel across the Tasman Sea and central NZ is likely on Tuesday and Wednesday.

Another slower moving HIGH is likely from Friday to Sunday.


For NZ and Tasman Sea

On Friday to Sunday NZ got some rain from the subtropics.  Very welcome for the farmers with parched pastures but off-putting to the holiday-seekers.

Next trough is likely to be a LOW deepening off northern New South Wales on Wednesday and crossing NZ on Friday /Saturday.


See my yotpak at for terms used.

See my website for information on tailor-made voyage forecasts–

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